diff --git a/src/search.cpp b/src/search.cpp
index 36329f8f..14de2377 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -380,7 +380,7 @@ void Thread::search() {
           if (rootDepth >= 4)
           {
               Value prev = rootMoves[pvIdx].previousScore;
-              delta = Value(17);
+              delta = Value(17) + int(prev) * prev / 16384;
               alpha = std::max(prev - delta,-VALUE_INFINITE);
               beta  = std::min(prev + delta, VALUE_INFINITE);